Method and apparatus for exciting atoms in fluids



M. R. ANNIS ErAl. 2,920,201

APPARATUS FOR EXCITING ATOMS IN FLUIDS Filed Nov. 18, 1957 Jan. 5, 19601METHOD AND INVENTOR. MAX R. A'NNIS, FRED A. BROOKS JR.

4M4 xTaM ATTORNEY.

United States Patent METHOD AND APPARATUS FOR EXCITING ATOMS IN FLUIDS.Max R. Annis, Baytown, and Fred A. Brooks, In, Houston,,Tex.,assignors, by mesne assignments, to Jersey Production ResearchCompany,Tulsa, Okla., a corporation of Delaware Application November 18, 1957,Serial No. 696,979 5 Claims. (Cl. 250-495 sparking method.

Atoms can be raised from their normal state to higher energy states bybombarding them with electrons, or by subjecting them to hightemperatures in a flame 'or an electric arc, or by allowing them toabsorbradiant energy from an external source. A higher than normalenergy state is generally referred to as an excited state; When theatoms return to a state of lower energy, radiation is emitted in theform of photons of very definite frequency.

The emission spectrograph is commonly used for the analysis of chemicalelements and occasionally for the analysis of certain chemicalcompounds. The sample atoms and molecules are first excited. Uponreturning to normal they emit the characteristic radiations in the formof light rays. These light rays are passed through a lens system, acollumation system, a ditfraction grating, and then usually displayed ona photographic plate. The light rays are recorded on the photographicplate as vertical lines at a position determined by the frequency of thelight. The frequency of any line of the emission spectrum isproportional to the difference between the values of the energies of twostates of the atom or molecule emitting the radiation; that is,

Where 1 is the frequency of the light, E is the initial energy of theatom or molecule; E is the final energy of the molecular or atom, and his the Planck constant.

The invention described herein is a new method and apparatus forexciting atoms of a fluid by arcing method. In using the arcing method,a voltage isdeveloped across a pair of electrodes having suflicientenergy to excite the atoms of a fluid to be investigated.

A disadvantage of current methods of exciting atoms of a sample by themeans of the arcing method is that unwanted background appears andcontaminates the photographic plate, thereby interfering'with thedetection of the desired light rays. This unwanted background arisesfrom the interaction of the material the electrodes are made of withelements of the air contained in the arc. For example, with carbonelectrodes, the carbon of the electrodes and the nitrogen atoms of theair are violently thrown together and frequently combine. In the processof combining and disassociating, the CN molecules give ofi a very largenumber of bands of light rays that are poorly resolved which give riseto an unwanted background. The unwanted background produced thereby iscommonly referred to as the cyanogen bands. These bands may range from3590 to 3583, 3883 to 3850, and 42l6'to 4152 angstroms. In actualoperation, this background appears as a universal darkening throughoutmuch of the wave length region of interest on the photographic plates.

is contained in the chamber 14. This fluid may suitably In attempting todetect the presence and darkness of an individual line representative ofa specific chemical element, it is necessary to clearly distinguish thisline from the unwanted background. The cyanogen band makes thisdiflicult and consequently prevents the detection of lines caused bysmall amounts of a given chemical element which produces very lightemission lines. For example, the cyanogen band interferes with thedetection of small amounts of rubidium. The emission line of rubidiumappears at 4202 angstroms.

This invention is a new method and apparatus for excit-' ing atoms of afluid sample which substantially eliminates; the production of unwantedbackground caused by the interaction of the material of the electrodeswith elements contained in the air in the arcing region. For example,our new method and apparatus substantially eliminates the production ofthe cyanogen band when carbon electrodes are used. p

Briefly described, the method consists of providing a continuous supplyof liquid to each electrode. The sample fluid may be supplied to bothelectrodes, or in the alternative, to one electrode with distilled watersupplied to the other. A voltage is then applied across the electrodesof sufficient magnitude to excite the atoms in the fluid sample tohigher energy states.

One type of apparatus which is used in carrying out the new methodincludes a means for placing fluid on both electrodes. Means areprovided for producing a voltage across the electrodes (which have fluidthereon) suflicient to excite the atoms in the fluid sample to a higherenergy state.

A better understanding of the invention, as well as its many advantages,may be had by reference to the detailed description to follow and thesingle figure which shows a schematic drawing of our new apparatus forcarrying out our new method.

The figure shows a first electrode 10 which is supported by an electrodesupporting member 12.

Electrode 10 may be substantially cylindrical in shape and has a fluidchamber 14 formed therein. Some fluid be the solution to be analyzed ormay be distilled water.

The electrode 10 may be made of carbon, which is a preferred material.The use of carbon insures excitaton of all of the elements of the fluidsample. Also, the carbon is porous, thus permitting the fluid in chamber14 v to difiuse through the porous tip 16 of the electrode 10.

A fluid container support 18 is positioned below the electrode support12. A fluid sample container 20 is disposed on container support 18. Aportion of the fluid to be analyzed is placed in the fluid container 20.

A rotatable disc electrode 22 is mounted in spaced relation below thecylindrical electrode 10. The rotatable disc electrode 22, which ispreferably also made of carbon, is disposed so as to dip into the fluidin container 20 and carry some of the fluid into the region betweenelectrodes 10 and 22.

Voltage of sufficient magnitude to excite all of the atoms of the fluidis applied across the electrodes 10 and 22 to produce an arc in thearcing region between said electrodes. This is shown schematically by anAC. voltage source 24 having one terminal thereof connected to electrode10 through line 26, and the other terminal connected to electrode 22through line 28.

By providing means for placing fluid on both ofthe electrodes 10 and 22,the fluid sample is excited without the production of the unwantedassociation and disassocia- .It is to be understood that variousmodifications may be made in the foregoing method and apparatus withoutdeparting from the scope of the appended claims.

We claim:

1. An apparatus for use .in exciting the atoms of elements of a liquidsample comprising: a substantially cylindrical electrode having achamber in which some liquid is contained, said electrode being porousto permit liquid flow toward an end thereof; a container for holdingsome of the sample liquid; a rotatable disc electrode mounted in spacedrelation to the cylindrical electrode and disposed so as to dip into thesample liquid in said container and carry some of the sample liquid intothe region between said two electrodes; and means for producing avoltage across the electrodes sufiicient to excite the atoms of thesample liquid in said region to a higher energy state.

2. An apparatus in accordance with claim 1 wherein said electrodes aremade of carbon.

3. A method of exciting atoms of elements of a liquid sample by thearcing method using two spaced electrodes comprising the steps of:providing a continuous supply of liquid to one electrode and acontinuous supply .of sample liquid to the second electrode; andapplying a voltage across the electrodes suflicient to excite the atomsin the sample liquid to higher energy states.

4. A method of exciting atoms of elements of a liquid sample by thearcing method using two spaced electrodes comprising the steps of:providing a continuous supply of distilled water to one electrode and acontinuous supply of sample liquid to the second electrode; and applyinga voltage across the electrodes sufiicient to excite the atoms in thesample liquid to higher energy states.

5. A method of exciting atoms of elements of a liquid sample by thearcing method using two spaced electrodes comprising the steps of:providing a continuous supply of sample liquid to one electrode and acontinuous supply of sample liquid to the second electrode; and applyinga voltage across the electrodes sufiicient'to excite the atoms in thesample liquid to higher energy states.

References Cited in the file of this patent UNITED STATES PATENTS2,344,719 Nusbaum et al. Mar. 21, 1944 2,643,574 Todd Ian. 30, 19532,753,479 Aughey et al July 3, 1956 OTHER REFERENCES Catalogue fromUnited Carbon Products Co., Inc..

circa-.March .1955, R0. Box 269, Bay City, Michigan.

